Top National Hunt trainer Nicky Henderson has been charged by the British Horseracing Authority (BHA) after a horse he trains for the Queen failed a drugs test.

Mr Henderson will face the BHA’s disciplinary board in June and could get a substantial fine, or even a suspension.

Six-year-old Moonlit Path tested positive for the banned substance tranexamic acid after her debut race at Huntingdon in February.

The horse finished sixth in the mare’s novice hurdle, but a subsequent urine test revealed the presence of the drug.

Tranexamic acid is used to prevent haemorrhaging. Although it can be used legally in training, it must not be in the horse’s system on a raceday.

The Seven Barrows trainer has been charged with a breach of three rules.

Mr Henderson has been charged with a breach rules in that he “allowed or caused to be administered, or connived at the administration of, tranexamic acid, under the brand name Cyklokapron, to the mare either with the intention of affecting her racing performance or in the knowledge that her racing performance could be affected by such.”

The disciplinary panel will also consider whether the racehorse trainer “allowed the substance to be given to the mare by injection on the morning of racing, without seeking and obtaining dispensation from a veterinary officer” and that he “failed to keep a record of ‘a treatment’”.

In a statement, Mr Henderson said: “Unfortunately Moonlit Path tested positive for a prohibited substance after finishing sixth on her debut at Huntingdon.

“The substance concerned was administered by my vet entirely in the interests of the horse’s welfare, which is always paramount. There was no intention to enhance performance and it is worth pointing out that we won the race in question with the odds-on Ravello Bay.

“We have co-operated fully with the BHA throughout their investigation and I would prefer to make no further comment before the hearing.”

The Queen has been informed.